The present invention relates generally to electronic devices having displays, and more particularly to electronic devices that implement methods of touch location.
Touch-sensitive displays are commonly used in many different types of electronic devices. As is known in the art, touch-sensitive displays are electronic visual displays configured to detect the presence and location of a user's touch within the display area. Conventionally, touch-sensitive displays detect the touch of a human a finger or hand, but may also be configured to detect the touch of a stylus or of some other passive object. Although there are many different types of touch-sensitive devices, many are configured to detect a user touch by sensing pressure, detecting a change in resistance, or by measuring an amount of reflected light, for example.
Additionally, devices may now determine the location of a user touch by performing a passive sonic analysis of the noise that is made when the user touches the display. In practice, the device includes two microphones placed in carefully selected locations on the surface of the display. When a user touches the display, the microphones capture and analyze the acoustical signatures produced by the touch to determine the location of the touch. For example, the devices may compare the captured acoustic signature to a table of predetermined acoustic signatures that correspond to different locations on the display. If a match is found, the device has determined the location of the user touch.
Although useful, passive acoustic methods of locating the position of a user touch on a display remain problematic. For example, because a user may touch the display at any time, the audio processing function that analyzes the resultant sound must be active all of the time. These types of solutions require a significant amount of power, due both to the sensors and, more importantly, to a processor executing sound analysis software. For smaller, battery-powered devices, such as cellular telephones, this extra power consumption means that the device will require either a larger battery or more frequent recharging, neither of which is desirable from the user's perspective.
Another problem with passive methods is that the display and/or the integration of the requisite mechanical components (e.g., the microphones) must be unique for each model of the device. This is because the ability of the passive acoustic methods to determine the location of a user touch varies across the surface of the display. Consequently, each model must undergo an analysis to determine the correct positioning for both microphones as well as the relationship between the acoustic signatures and the location of the touch.
Further, passive acoustic methods necessarily require a sound to be made when the user touches the display surface. This does not always occur when the user touches the display with a finger. Additionally, even when the microphones do detect the sound of a user touch, the accuracy of any given passive acoustic method may vary with the force of the touch. Moreover, passive acoustic methods may be computationally complex and slow since they involve searching tables of predetermined signatures to obtain one that most closely resembles the captured acoustic signature. Often times, such methods may not be able to provide a closed or unique solution.
Currently, some devices now utilize haptic technology (i.e., “haptics”) to render feedback to the user. Haptics is a tactile feedback technology that applies forces, vibrations, and/or motions to a user by vibrating or shaking a display being touched by the user. The devices that cause the vibrations are called “haptic transducers.” The user senses these vibrations and perceives them as if the user had depressed a key on a keyboard, for example. Although haptics may be used to induce the user's perception that a key has been depressed, it is not known for use in determining the specific location of a user touch.